Mitosis or Meiosis?
This represents a tiny embryo just beginning to form. Once an egg is fertilized, the resulting
single cell must divide many, many times to develop a fetus. Both mitosis and meiosis involve
cell division; is this type of cell division an example of mitosis or meiosis? The answer is
mitosis. With each division you are making a genetically exact copy of the parent cell, which
only happens through mitosis.
Mitosis vs. Meiosis
Mitosis, meiosis, and sexual reproduction are discussed at
http://www.youtube.com/watch?v=kaSIjIzAtYA (18:23).
Both mitosis and meiosis result in eukaryotic cells dividing. So what is the difference between
mitosis and meiosis? The primary difference is the differing goals of each process. The goal of
mitosis is to produce two daughter cells that are genetically identical to the parent cell, meaning
the new cells have exactly the same DNA as the parent cell. Mitosis happens when you want to
grow, for example. You want all your new cells to have the same DNA as the previous cells. The
goal of meiosis, however, is to produce sperm or eggs, also known as gametes. The resulting
gametes are not genetically identical to the parent cell. Gametes are haploid cells, with only half
the DNA present in the diploid parent cell. This is necessary so that when a sperm and an egg
combine at fertilization, the resulting zygote has the correct amount of DNA—not twice as
much as the parents. The zygote then begins to divide through mitosis.
Pictured below is a comparison between binary fission (Figure below), which is cell division of
prokaryotic organisms, mitosis, and meiosis. Mitosis and meiosis are also compared in the table
that follows (Table below).
A comparison between binary fission, mitosis, and meiosis.
Purpose:
Mitosis
Meiosis
To produce new cells To produce gametes
Number of cells produced:
2
4
Rounds of Cell Division:
1
2
Haploid or Diploid:
Diploid
Haploid
Daughter cells identical to parent cells? Yes
No
Daughter cells identical to each other? Yes
No
Vocabulary
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binary fission: Reproduction through growth and division of the cell, as in bacteria.
daughter cells: Cells that result from division of the parent cell during mitosis or
meiosis.
diploid: Having two sets of chromosomes; 2n.
fertilization: Union of a sperm and egg.
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gamete: Sex cell, such as sperm or egg.
haploid: Having one set of chromosomes, as in sperm and egg; n.
meiosis: Process in cell division that reduces the chromosome number in order to make
gametes.
mitosis: Process in cell division during which the nucleus divides so that a new cell is
produced that is identical to the parent cell.
zygote: Cell that forms when a sperm and egg unite; the first cell of a new organism.
Summary
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The goal of mitosis is to produce a new cell that is identical to the parent cell.
The goal of meiosis is to produce gametes that have half the DNA of the parent cell.
Practice
Use the resources below to answer the questions that follow.
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Mitosis and Meiosis Simulation at http://www.youtube.com/watch?v=zGVBAHAsjJM
(11:53)
1.
2.
3.
4.
What are homologous chromosomes?
How do the location of specific genes compare between homologous chromosomes?
What is a tetrad? Why are they an important feature of meiosis?
How does meiosis differ between females and males? Why do you think this is? Explain
your reasoning as much as possible.
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How Cells Divide at http://www.pbs.org/wgbh/nova/body/how-cells-divide.html
1. How many daughter cells arise from mitosis? How many daughter cells are produced in
meiosis?
2. How is the location of the chromosomes during prophase of mitosis different from their
location during prophase I of meiosis? Why is this difference significant?
3. How does the attachment of spindle fibers differ between mitosis and meiosis?
4. Is anaphase I or anaphase II in meiosis more analogous to anaphase in mitosis? Explain
your reasoning.
5. How many steps are there in mitosis? How many steps are there in meiosis?
6. How does interphase I of meiosis differ from interphase II of meiosis?
Review
1. What is the goal of mitosis? Of meiosis?
2. How many cells are created during mitosis? During meiosis?